Project COMBATTING BIOCHEMICAL ATTACKS

It's probably just a matter of time until terrorists stage another biochemical attack similar to the one that shocked the world in 1995, when members of a Japanese religious cult released sarin, a deadly nerve gas, in a Tokyo subway station. Twelve people died. The Pentagon also anticipates that biochemical weapons may be used by future adversaries trying to offset the technological superiority of U.S. forces.

The acetylcholinesterase enzyme (above) is monitored by the sensor because it
is the main target of neurotoxins.

Nerve gases and other neurotoxins are especially dangerous since they assault the nervous system, causing vital organs to shut down. Without an antidote, death usually follows in minutes. Quick detection of biochemical agents is thus essential--and David has designed a dexterous sensor to detect every major neurotoxin.

His sensor monitors the state of the acetylcholinesterase (AChE) enzyme, the main target of neurotoxins. It uses a setup analogous to a nanoscale light bulb, dimmer switch, and battery. A new type of quantum dot--a crystal only a few dozen atoms wide, composed of a semiconductor such as cadmium selenide--supplies the juice, while AChE serves as the dimmer, and a small chemical-dye molecule attached to the enzyme is the light bulb. When a neurotoxin is present, the AChE absorbs some of energy flowing from the quantum-dot battery to the dye molecule, dimming its glow and signaling danger.

Next, David hopes to fine-tune the dimmer function so that the level of light points to a specific neurotoxin. Meanwhile, a paper on the new type of quantum dots has been submitted to Physical Review B, and another will be presented this May at CLEO, or Conference on Lasers & Electro-Optics.